CILOCK

The CILOCK system initialization parameter specifies whether CICS® should keep the control interval lock of a record-level sharing (non-RS) Virtual Storage Access Method (VSAM) file after a successful read-for-update request.

For VSAM data sets creation and usage, see VSAM data sets. For performance tuning issues related to VSAM and file control, see VSAM and file control: improving performance.

Defining CILOCK

You can define the CILOCK system initialization parameter in the following ways:
  • In the PARM parameter of the EXEC PGM=DFHSIP statement.
  • In the SYSIN data set of the CICS startup job stream.
  • Through the system console.
  • In the DFHSIT macro.

Values for CILOCK

CILOCK={NO|YES}
Valid values for the CILOCK system initialization parameter are as follows:
NO
NO is the default value for CILOCK and specifies that CICS should set the control interval free. This allows other tasks to access other records in the same control interval, without an exclusive control conflict occurring. In these cases throughput should be greater. Note that the record lock on the record for which the read-for-update was first issued, still prevents other tasks from updating this record, even though the control interval lock has been released. When the record is rewritten or deleted, the read-for-update is reissued to VSAM as part of the update processing.

If a WRITE is issued by another task during a READ UDPATE, the WRITE receives a DUPREC condition.

YES
YES specifies that CICS cannot set the control interval free. This means that a subsequent rewrite or delete request does not need to reissue the read-for-update request to VSAM. However, if other tasks attempt to access other records in the same control interval, an exclusive control conflict occurs on this control interval, forcing these tasks to wait until the update request completes.